Measurements, Mechanisms, and Models of Heat Transport

Anne M. Hofmeister

• Publisher: Elsevier
• Year: 2018
• Print ISBN: 9780128099810
• eBook ISBN: 9780128099827
• Topic: Physical Sciences
• Subtopic: Geophysics

Measurements, Mechanisms, and Models of Heat Transport offers an interdisciplinary approach to the dynamic response of matter to energy input. Using a combination of fundamental principles of physics, recent developments in measuring time-dependent heat conduction, and analytical mathematics, this timely reference summarizes the relative advantages of currently used methods, and remediates flaws in modern models and their historical precursors. Geophysicists, physical chemists, and engineers will find the book to be a valuable resource for its discussions of radiative transfer models and the kinetic theory of gas, amended to account for atomic collisions being inelastic. This book is a prelude to a companion volume on the thermal state, formation, and evolution of planets.Covering both microscopic and mesoscopic phenomena of heat transport, Measurements, Mechanisms, and Models of Heat Transport offers both the fundamental knowledge and up-to-date measurements and models to encourage further improvem- Combines state-of-the-art measurements with core principles to lead to a better understanding of heat conduction and of radiative diffusion, and how these processes are linked- Focuses on macroscopic models of heat transport and the underlying physical principles, providing the tools needed to solve many different problems in heat transport- Connects thermodynamics with behavior of light in revising the kinetic theory of gas, which underlies all models of heat transport, and uses such links to re-derive formulae for blackbody emissions- Explores all states of matter, with an emphasis on crystalline and amorphous solids

Chapter 1

The Macroscopic Picture of Heat Retained and Heat Emitted

Thermodynamics and its Historical Development

Anne M. Hofmeister and Robert E. Criss

Abstract

This introductory chapter provides the fundamentals needed to understand heat and its idealized, time-independent transfer, as a prelude to understanding heat flow, which is strongly time-dependent. The macroscopic nature depiction of light is introduced in this chapter. Because the equivalence of light and heat was demonstrated subsequent to the development of the first and second laws of thermodynamics, the classical physics depiction of light has not been adequately incorporated in basic discussions of heat and thermodynamics. This omission is evident in the 1800s focus on reversibility, and it impedes the realistic description of many large-scale processes. Some thermodynamic concepts and models that are important to natural sciences and engineering are based on incomplete or incorrect statements in the literature, and/or rely on the unrealistic ideal gas or nonexistent reversibility. This chapter attempts to address and manage those inconsistencies, in part by drawing attention to missed connections.

Keywords

Thermodynamics; conservation principles; heat; light; temperature; entropy; radiation; macroscopic behavior; reversibility; adiabats

Outline

• 1.1 Energy and the First Law of Thermodynamics 3
  • 1.1.1 Conversion of Mass to Energy 5
  • 1.1.2 Temperature Differs from Heat 6
  • 1.1.3 Volume, Pressure, and the Equation of State 6
  • 1.1.4 Heat Capacity, Enthalpy, and Latent Heat 8
  • 1.1.5 Types of Work 9
  • 1.1.6 Understanding Frictional Heating Requires the First Law 9
• 1.2 Entropy and More Laws of Thermodynamics 10
  • 1.2.1 Reversibility, Thermal Equilibrium, and the Zeroth Law 11
  • 1.2.2 Isothermal vs Adiabatic 12
  • 1.2.3 Entropy Defined 13
  • 1.2.4 Entropy, Heat, and the Third Law 17
  • 1.2.5 State Functions, Variables, and Interrelationships 17
  • 1.2.6 Compression and Expansion of an Ideal Gas 21
  • 1.2.7 Is the Third Law Complete? 25
• 1.3 The Relationship of Light and Heat 26
  • 1.3.1 Studies Beyond the Rainbow in the 1800s 27
  • 1.3.2 Characterization of Emitted Light 27
  • 1.3.3 Connection of Blackbody Radiation to Temperature 29
  • 1.3.4 Radiation and Thermodynamic Laws 30
  • 1.3.5 Ballistic vs Diffusive Transfer 32
  • 1.3.6 Momentum and Pressure of Light 32
• 1.4 Summary 32
• References 33

The progress of science … is not wholly unlike a pack of hounds, which in the long run perhaps catches its game, but … the louder voiced bring many to follow them nearly as often in a wrong path as in a right one; where the entire pack even has been known to move off bodily on a false scent.

Samuel Pierpont Langley (1889)

You can’t unfry an egg, but there is no law against thinking about it.

Don Herold (1953)

The macroscopic perspective is always the starting point in scientific endeavors because this consists of a simple description of things that we can measure or sense. The macroscopic picture is inseparable from laboratory measurements. Importantly, no special assumptions need to be made about the nature of matter and only a relatively small number of quantities need to be considered. Much of the material on macroscopic, classical thermodynamics presented in this chapter will be familiar to the reader, but our approach diverges from most presentations by drawing attention to flaws and inconsistencies in historic analyses. Although modern studies have remediated many of the incorrect historic analyses, misconceptions remain and some current paradigms in heat transfer, geophysics, planetary science, and astronomy are underlain by historic errors.

Heat is energy, the nature of which is long debated. Idealized, time-independent transfer of heat (and its tie to work) is the basis of thermodynamic laws. The equilibrium, conservative, static, and idealized processes covered in this chapter greatly differ from the disequilibrium, diffusive, and dissipative conditions causing real heat flow, which is time-dependent: the macroscopic picture involving time is covered in Chapter 3. We also need to understand how energy in its purest form (light) moves and how it interacts with material: basic material is given in Section 1.3 and is developed further in Chapter 2. These three chapters provide a self-contained statement of the classical physics underpinnings, which is predominantly macroscopic.

The field of physics developed through explaining experimental data: this approach is used to understand heat transfer in this book. Much of current understanding of thermodynamics and heat is based on (1) analogs between thermal and mechanical behavior and (2) experiments and models for gas behavior, which are covered in many textbooks on thermodynamics (e.g., Zemansky and Dittman, 1981; Richet, 2001). The present book covers gas behavior where it differs from solid behavior: the difference can be crucial. We consider behavior of mass, because mass diffusion is similar to heat diffusion, but easier to understand in many ways. Although this chapter does not quantify time-evolution, the fact that time is involved in any process needs to be discussed. Variables and abbreviations are defined when introduced, and are compiled in Appendix A for convenience of the reader.

Section 1.1 explores our understanding of heat and conservation laws from classical thermodynamics. Section 1.2 concerns entropy and its connection to heat and space occupied. The role of space has been short-changed in classical discussions, because steam engines were the key technological problem of the 1800s. Section 1.3 covers emissions from hot bodies, emphasizing that acceptance of visible light and heat emissions being the same phenomenon postdates classical thermodynamics. The out-of-synch developments explain why radiative transfer was not incorporated in historical and seminal works on thermodynamics. Inadequately considering volume, overemphasizing reversibility, and omitting radiative loss have consequences for problems on diverse scales.

1.1 Energy and the First Law of Thermodynamics

Physics rests on universal principles. Among the most important are conservation laws, which were developed over many centuries, and are essential to understand heat and its transport. To discuss conservation, it is necessary to differentiate between a system (what we are interested in) and its surroundings (which we tend to ignore, but should not). We are primarily interested in closed systems, which exchange energy but not matter with the surroundings. Isolated systems, which exchange neither matter nor energy, and open systems, which exchange both, are relevant in some circumstances. These classifications exist because the behavior of the surroundings is important. These various exchanges, as noted above, are considered in terms of the initial and final states, and thus are commonly treated as being more-or-less instantaneous (Fig. 1.1). Great care must be taken in consideri...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Preface
• Chapter 1. The Macroscopic Picture of Heat Retained and Heat Emitted: Thermodynamics and its Historical Development
• Chapter 2. Macroscopic Analysis of the Flow of Energy Into and Through Matter From Spectroscopic Measurements and Electromagnetic Theory
• Chapter 3. The Macroscopic Picture of Diffusive Heat Flow at Low Energy
• Chapter 4. Methods Used to Determine Heat Transport and Related Properties, With Comparisons
• Chapter 5. Reconciling the Kinetic Theory of Gas With Gas Transport Data
• Chapter 6. Transport Behavior of Common, Pourable Liquids: Evidence for Mechanisms Other Than Collisions
• Chapter 7. Thermal Diffusivity Data on Nonmetallic Crystalline Solids from Laser-Flash Analysis
• Chapter 8. A Macroscopic Model of Blackbody Emissions With Implications
• Chapter 9. Transport Properties of Metals, Alloys and Their Melts From LFA Measurements
• Chapter 10. Heat and Mass Transfer in Glassy and Molten Silicates
• Chapter 11. Modeling Diffusion of Heat in Solids
• Chapter 12. Conclusions and Future Work
• Appendix A. Conventions, Abbreviations, and Variables Used
• Appendix B. Guide to Electronic Deposit of Thermal Diffusivity Data
• Appendix C. Summary of the Literature on Heat Capacity and Density (or Thermal Expansivity) as a Function of Temperature
• Index